The present invention relates generally to sound generating signal units such as loud speakers and tone generators, and also relates to buzzers, vibrators and devices used for generating a vibration or inertial signal which may be felt or sensed while not producing a highly audible sound. Assemblies of this latter type in the prior art are used, for example, to signal a query by or an active state of a beeper, pager or alarm system, or to otherwise indicate an attention-getting state of a consumer device.
A number of reasonably inexpensive and effective constructions have evolved in the prior art for providing signal units to generate the necessary tones or vibrations for these devices. These include miniature motors with imbalanced rotors to create a sensible vibration; small piezo electric assemblies to vibrate at an audio frequency and create a tone or beep noise; and other, older technologies such as speakers with an electromagnetic voice coil, or a magnetic solenoid driving a diaphragm to create a sound such as an audio tone or a vibratory buzz.
In general, each of these technologies or its method of incorporation in a device has certain limitations such as requiring a high voltage driver or a relatively high current driver; imposing penalties of weight and/or size; increasing the difficulty or cost of assembly into the electronic apparatus in which it is to operate; or requiring special engineering to increase the hardiness or lifetime of the device when installed for its intended conditions of use.
Thus, for example, as applied to an item such as a hand-held pager, which is required to be of extremely small size and low electrical power consumption, yet which is frequently dropped and subject to extreme impact, the defined constraints do not favor either electromagnetic motors, which require a comparatively large amount of electrical power, nor piezoelectric elements, which are sensitive to shock and generally require a case or other structural support to sustain vibration without suffering electrode detachment or crystal breakage. Nonetheless, such sub-assemblies are commonly used in devices of this kind.
Moreover, piezoelectric assemblies have been used for a variety of tone-generating tasks, both in earphones, and in larger, more complex, speaker constructions. In U.S. Pat. No. 5,638,456 one method has been proposed for placing piezo elements on the cover or housing of a laptop computer to form an audio system for the computer. Proposals of this type, however, must addresss not only the problems noted above, but may be required to achieve a degree of fidelity or uniformity of response over their tonal range which is competitive with conventional speaker technologies. Such a goal, if achieved, may be expected to necessitate an unusual mounting geometry, a special cavity or horn, a compensated audio driver, or other elements to adapt the piezo elements to their task or enhance their performance. Thus, not only the sound generator, but its supporting or conditioning elements may require mounting in the device, and these may all require special shaping or other adaptation to be effectively connected to, or to generate signals in, the device.
There is therefore a need for an efficient and durable signal generator which is better suited to the electrical devices of modern consumer taste.
Accordingly, it would be desirable to provide an improved signal generator effective for producing audio or inertial signals.
It would also be desirable to provide a sound/inertial unit of simple construction but readily adapted to device housings of diverse size and shape.
It would also be desirable to provide a sound/inertial unit of simple construction but adapted to processes of manufacture with the device housing.
It would further be desirable to provide such a sound or inertial generator assembly adapted to simplified and more effective installation in a consumer device.
These and other features are obtained in an audio/inertial signal generator in accordance with the present invention, wherein an actuator includes an electrically actuable member formed of a material such as a ferroelectric or piezo material, which generates acoustic or mechanical signals and is mechanically in contact with a body of polymer material. In one embodiment the member is assembled to a region of a wall or surface, for example, of a housing, and imparts energy thereto. The electrically actuable or piezoelectric member, which may for example cover a region having a dimension approximately one half to three or more centimeters on each side, is preferably compression-bonded to one or more electroded sheets, such as flex circuits, or to a patterned metal shim or the like, which enclose and reinforce the material while providing electrical connection extending over the signal generation unit. The lamination or compression bonding provides structural integrity, for example by stiffening or binding the member, and prevents structural cracks and electrode delamination from developing due to bending, vibration or impact. This construction strengthens and enables the piezo member, which is preferably a sheet or layer with relatively large length and width dimensions compared to its thickness, to be actuated as a single body and engage in vibration or relatively fast changes of state, or more generally, to produce electrically driven displacement, deformation or vibration of the device. That is, it effectively transmits acoustic or mechanical energy through the housing to which it is attached. The structure is adapted for assembly or forming with the housing, and may be installed by cementing together or by a spot fastening process. Preferably, however, the actuable member is formed with or manufactured into the wall or housing by a process such as injection molding wherein the molded body of the device is formed into all or part of a bounding surface of the signal generator, or wherein a solid block of polymer holds the actuable assembly and is itself joined to the housing by fasteners or compatible bonding agents.
The piezo member has the form of a thin layer or sheet, which may extend in a branched or multi-area shape, and may be fabricated with both mechanically active regions and non-mechanically active, or xe2x80x9cinactivexe2x80x9d, regions. The active regions contain electroded electroactive material, whereas the inactive regions may be regions disjoint from the mechanically active regions and may be shaped or located to position and provide structural support and/or electrical pathways, e.g., mounting hole and electrical lead-in connections, to the active regions. The inactive regions may include non-electroded electroactive material, or may lack the material altogether and contain only electrical lead-ins, cover film, or the like. Portions of the signal unit may be pinned in an injection mold and a device housing then molded about or adjacent to the unit, or else may be positioned and then cemented or thermally bonded to the housing after the housing has been molded, thereby simplifying fabrication of the final device. In one embodiment, the signal unit is a vibrating beam or sheet which may be pinned, clamped or otherwise attached at one or more positions along its length, leaving a portion free to displace and create inertial impulses which are coupled to the housing at the fixed or clamped portion. In that case, the fixed portion may be defined by a block of polymer material molded about the electroactive assembly, thus providing an inert and machinable or clampable region for affixing to the device. In another embodiment, the unit is fastened to or contained within a wall of the device""s housing, and couples energy thereto such that the wall acts as a tone-radiating surface. The unit is preferably mechanically connected over a major portion of its surface and activated to produce waves in the attached housing, so that the housing itself forms a novel radiating surface. The signal assembly may have plural separate active regions which are connected, in common or separately, to different portions of the housing wall, and which may be operated variously as sensing switches, audio speakers covering one or more frequency bands, or tactile sub-audio signal indicators. The separate active regions may also be attached to the housing at separated positions and be driven in phased relation to more effectively create particular excitations of regions of the wall , or may be driven as independent pairs to produce stereo sound.
In one exemplary embodiment, the housing is the housing of a laptop or other computer, and the signal assembly includes two flat piezo transducers, each having one or more active regions for producing audio vibration, and which are co-fabricated with the housing by a molding or thermal bonding assembly process to form stereo audio emitters. In another embodiment, the housing is the body of a computer mouse and the generator is coupled to provide sensible disturbances in a button or face of the mouse, or to sense applied force and produce an electrical signal therefrom. In yet another embodiment, a generator is coupled to the housing of a pager or cellular phone in a manner to flex the thin housing wall, such that the housing provides both an inaudible inertial stimulus, and an audibly projected tone for signaling the user, optionally with a strain sensing functionality.
A method of manufacture includes designing a flexible piezoelectric package having an active region with a two-dimensional shape matching one or more faces of a housing, and attaching the package to the housing such that the face or faces radiate audio and/or inertial vibration when the package is energized. A region of the package may also act as a control transducer when the housing is stressed.